Metal-casting or metal-pouring ladles or like vessels of the bottom-discharge type may be provided with a pouring spout in the form of a passage extending through the ladle lining and shell of the ladle and closed therebelow by a linearly or rotatably shiftable slider having an opening which can be aligned with or brought into registry with this passage.
To seal the spout against the high temperature molten metal when the opening in the slider is offset from the passage, i.e. in the closed position of the spout valve or closure, the passage can be filled by a so-called filling mass of pulverulent or other comminuted form. This mass is supported within the passage by the slider and is piled above the top of the passage to form a heap which extends outwardly beyond the passage and is adapted to contact the molten metal when the latter is poured into the ladle.
Upon alignment of the slider opening with the passage, this mass can be discharged and the passage cleared.
Such spout-filling masses can be used for the discharge passages, nozzles or outlets of ladles used for the handling or treatment of various metals, e.g. commercial steels and even specialty steels such as stainless steel, as well as for other metals.
While filling masses of the aforedescribed type have proved to be effective in protecting the slider, certain problems are encountered when they are used. For example, the opening operation with conventional filling masses is not reliable, i.e. a fixed flow cross section and rate of opening frequently cannot be guaranteed because such masses tend to sinter or fuse in a more or less uncontrolled manner so that obstructions remain when the slider opening is brought into registry with the passage. Frequently the entire mass fuses into a rigid and nonflowable structure so that it must be broken out with a time-consuming and hence expensive series of operations. In other cases, the passage may remain partly obstructed which is disadvantageous with respect to the pouring operation and subsequent treatment of the melt.
In general, therefore, the use of earlier filling masses has been found to be fraught with problems which have been associated with high casting costs, unreliable performance and dangerous conditions such that the casting operation as a whole can be adversely affected.
Conventional filling masses include quartz sand, chromite zirconia, magnesite, iron oxide, titanium dioxide or mixtures thereof.
It should also be noted that conventional masses can effectively be used only under very limited sets of operating conditions empirically determined for each mass. In other words, any particular mass does not have general applicability.
Reference may be had to German Printed Application DE-AS 14 58 180 which describes a spout-filling mass consisting exclusively of quartz and anthracite coal (column 3, lines 8 through 10).
Experience with this system has shown that opening of the spout cannot be guaranteed, i.e. the movement of the closure plate to align its opening with that of the spout for exchange of melt poses a problem.
In some cases, flow does not automatically commence so that considerable manipulation is necessary to start the discharge.
Furthermore, for any effective use of this system it is necessary to provide a special geometry of the spout which also is an expensive proposition.